This invention relates to processes for the production of tools for manufacturing operations. The tools of interest in this particular application are those which are used to mold, emboss or print a surface with a desired pattern. The tools, which are referred to hereinafter as xe2x80x9cpattern-forming toolsxe2x80x9d, can have the form of a roll in which the surface has the desired pattern, or a simple plate or a belt with the pattern formed on the surface.
The main interest for the present invention is in the creation of tools that can be used to produce coated abrasives with surfaces engineered to produce specifically designed effects. The invention will be described with this subject matter as the principal focus but it should clearly be understood that the invention can readily be adapted to meet the needs of a wide variety of printing, shaping or embossing applications that have no direct connection to coated abrasives but which share a common need for a rapid, versatile and economic technique for the production of tools with complex patterns formed on the surface of the tool.
Coated abrasives with engineered surfaces are formed by depositing a layer comprising abrasive particles dispersed in a curable binder formulation. The binder is frequently but not essentially a radiation-curable binder and the abrasive particles can be any of those commonly used in coated abrasives including fused and sintered alumina, silicon carbide, alumina/zirconia, superabrasives such as cubic boron nitride, complex aluminum/magnesium borides and diamond, and softer abrasives intended for polishing softer materials such as glass including silica, alpha alumina precursors and ceria. The surfaces may be engineered by a molding or embossing or rotogravure deposition technique such are described for example in U.S. Pat. Nos. 5,014,468; 5,152,917; 5,840,088; and 5,863,306.
Often it is advantageous to provide that the surface comprises repeating shapes that may be exactly identical and regularly spaced but for many other applications it is desirable that the shapes be arranged in patterns that include shapes that are not the same and/or are not in a uniform pattern across the whole surface shaping tool. Such departures from the regular are found to be effective in avoiding the development of scratch patterns or scribing on the surface of the substrate being abraded. However the need for non-uniformity makes the production of the surface shaping tool, (which is commonly produced by knurling appropriate patterns on the surface of the tool), much more difficult and technically challenging where the knurling of a pattern of continuous straight lines across the tool surface will not produce the desired non-uniform pattern.
In addition the tool surface often represents a compromise since the expense of producing specifically designed tools for each application is considerable. A further complicating factor is that, because of the contact with abrasive materials, the life of a tool before it becomes eroded or otherwise deformed can be quite limited.
There exists therefore a need for a process for making surface-forming or shaping tools that is extremely versatile, speedy and economic. The present invention provides such a process and forming tools made by this process. The tool can be adapted for a range of processes including molding, embossing, rotogravure deposition and/or printing. As indicated above however, the main interest explored in the description of the invention that is provided herein is the production a tool suitable for making patterned, (or xe2x80x9cengineeredxe2x80x9d), coated abrasive products.
The present invention provides a process for the production of a coated abrasive having an engineered patterned surface characterized in that the pattern on the surface is generated using a tool produced by a rapid prototyping technique.
Coated abrasives having engineered patterned surfaces are generally coated abrasives having a substrate material and an abrasive layer deposited on the backing comprising abrasive particles dispersed within a cured binder. The abrasive layer has a surface engineered to have a pattern which generally provides a plurality of locations in which the thickness of the layer is greater than the average thickness of the layer. The pattern comprises regularly repeating units though within each unit the pattern may be somewhat randomized. Typical examples of coated abrasives with engineered patterned surfaces are described for example in U.S. Pat. Nos. 5,152,917; 5,454,844; 5,489,235; 5,658,184; 5,672,097; 5,681,217; 5,833,724; 5,840,088 and 5,863,306.
The techniques described for producing the patterned surfaces include rotogravure printing, embossing and molding. The tools therefore can be used for example as molds, embossing rolls or gravure rolls.
Other techniques involve the scribing of parallel triangular grooves in a tool then scribing more parallel grooves at right angles to the first leaving square-based pyramids on the surface. This surface can be used directly as the shaping tool or it can be used to mold the female equivalent variation. This technique is described in U.S. Pat. No. 5,300,263. Other processes inscribing or knurling a pattern on a roll include U.S. Pat. Nos. 4,478,769; 5,435,8116; 5,489,235; and 5,946,991. All such processes require the production of cutting tools and the tools must be continually and carefully aligned and the types of pattern that can be reproduced are strictly limited and aligned with each other between parallel lines.
The present invention permits unlimited versatility in the choice of pattern and is limited only to the extent the size of the surface that can be produced by a specific RPM machine is limited. Whatever the technique, the present invention requires the use of a tool that can be readily fabricated by a rapid-prototyping, (xe2x80x9cRPxe2x80x9d), technique and that can be used and discarded or replicated without considerable expense.